FtWorthless

Alright I have done a search for this already, so no flames please! This is my first post, BTW.

I can't seem to find a consistent answer on whether the turbo control actuator should cycle back and forth with key on/key off as the charge control actuator does. Some posts say it does, some posts say it doesn't. I am trying to diagnose a low-boost @ transition problem, and high boost on the primary turbo (completely stock car with Efini Y-pipe and PCV to UIM eliminated, just did full-on vacuum hose job which didn't fix problem). I believe the problem is the TCA or the Prespool, I haven't tee'd into the lines yet but I did crawl under the car and look at the TCA shaft.

After starting, running at WOT for a couple seconds, then at idle for a few seconds more, the KOKO sequence does not move the TCA at all. I had a friend do this while I was under the car. What does happen is that when the car is turned on the TCA pulls in, then almost immediately it snaps back shut. This I believe is correct - it will see vacuum as soon as the car is started, then the ECU will signal all the solenoids to their idle configuration, which for the TCA is closed (no vacuum or pressure applied), where it should remain until 4500 rpm. Now I don't know whether the KOKO sequence should cycle the TCA. When you shut off the car, should the solenoid open back up to send vacuum to the TCA, pulling it open? The CCA works fine, I get 8 KOKO cycles out of it. I get 19 in-Hg at idle, and the vacuum tank holds pressure, tested via MityVac and by pulling the hose off after the car is shut off.

So back to the basic question: does my TCA not cycling with the key indicate a problem or is this normal? The TCA moves pretty slowly when the car is started (no pressure on other side at idle, so that might not be a problem), and I've seen it pull in really small amounts or large amounts intermittently during in a 10 minute span of starting the car a few times. Don't know whether that might indicate a problem with the TCA, the hoses to it, the actuators or the ECU. It could mean I have the pressure side of the TCA accidentaly connected to vacuum, but I doubt it. As soon as I get a vacuum tee of the right size I'll know.

Anyone experienced enough to know whether the TCA should cycle, please help. Thanks!

SleepR1

According to this link:

http://www.autosportracetech.com/RX-...alBoostPattern

...the TCA AND the CCA should actuate each time with the Key Off/Key On sequence. If the TCA is not actuating then you might have a vacuum leak in the hose leading from the rat's nest to the TCA OR your TCA is bad. The fact that your CCA DOES actuate with the Key On/Key Off sequence tells me your vacuum chamber is ok--the vacuum chamber should provide enough vacuum to actuate the CCA AND TCA through @ least 6 KOKO sequences.

I suggest reading the entire link.

http://www.autosportracetech.com/RX-7/rx7stuff.htm

I used this link as my resource in diagnosing AND fixing my secondary boost problem with my J-spec twins.

Good luck!